In order to embed an electronic watermark for copyright management into digital data such as image contents, the embedded data should have resistance to various kinds of processing that the data experience after embedding. Above all, resistance to scaling processes, that is, enlargement and reduction operations, of images is important. Conventionally, in preparation for when the enlargement or reduction operation be performed to digital data with an electronic watermark embedded, one has coped with transformation operations of digital data by embedding calibration signals into digital data in addition to electronic watermark information in order to perform geometric compensation, and detecting the calibration signals. However, such a method requires embedding patterns for geometric compensation in addition to embedding information of the electronic watermark, thereby having possibilities to leading to deterioration in quality of original data or increase of detection time of embedded information.
Moreover, when patterns for geometric compensation are embedded in the frequency space, the inverse frequency conversion was required to detect them.